The prior art describes a wide variety of ultraviolet curable inks. For the most part, commercially acceptable UV curable inks employ a benzophenone photoinitiator. The main problem with the inks of the prior art is their relatively short shelf life - normally in the range of from 3 to 6 months, after which they were rendered useless, normally due to gelling.
It has been found that by employing a very specific combination of photoinitiators in conjunction with certain acrylated epoxy or urethane type oligomers that a commercially acceptable UV curable ink may be produced which has a shelf life of up to one year without substantial loss in cure speed and without undergoing polymerization when stored in the dark at room temperature.